1. Field of the Invention
The present invention relates to an engine provided with a crank mechanism and a balancer mechanism that inhibits vibrations caused by the crank mechanism.
2. Description of the Related Art
Conventionally, there is known an engine provided with a crank mechanism and a balancer mechanism that inhibits vibrations caused by the crank mechanism (see, for example, JP-A-2003-237674).
JP-A-2003-237674 discloses a scooter type motorcycle mounted thereon a uniaxial balancer mechanism for generation of an inertial force, which is reversed in direction to and has the same magnitude as that of a primary inertial force of a crank mechanism, in order to lessen vibrations caused by the primary inertial force of the crank mechanism.
Since the construction disclosed in JP-A-2003-237674 is set such that a vectorial locus of a primary inertial force of a crank mechanism is made a circle and an inertial force of a balancer mechanism is reversed in direction to and has the same magnitude as that of the primary inertial force of the crank mechanism in all phases, no translational force is generated by the primary inertial force of the crank mechanism and the inertial force of the balancer mechanism. Thereby, it is possible to inhibit vibrations caused by a translational force generated by the primary inertial force of the crank mechanism and the inertial force of the balancer mechanism.
Since a balancer shaft is arranged in a position spaced a predetermined distance from a crankshaft, a couple of forces is generated by the primary inertial force of the crank mechanism and the inertial force of the balancer mechanism. Since the couple of forces is generated with a center of gravity of an engine as an instantaneous center of rotation, there is a disadvantage that there are generated vibrations turning with the center of gravity of the engine as the instantaneous center of rotation. Hereupon, with the arrangement disclosed in the Patent Document JP-A-2003-237674, an engine is held through a link in order to prevent vibrations caused by the couple of forces from being transmitted to the engine. More specifically, with JP-A-2003-237674, in the case where the engine is supported in an optional position other than the center of gravity of the engine, vibrations are not prevented from being generated in this position but the link prevents transmission of vibrations to a vehicle body. That is, vibrations themselves caused by the couple of forces generated in a position, in which the engine is supported, are not controlled and inhibited.